Question

When a rectangular coil having length $ l $ and breadth $ b $ are placed perpendicular to the magnetic field. The torque experienced by the coil is:

• A. \( l b B \)
• B. \( \frac{1}{2} l b B \)
• C. \( l b B^2 \)
• D. \( l b B^2 \sin \theta \)

Hint:

When a coil is placed perpendicular to a magnetic field, the torque experienced is directly proportional to the area of the coil and the magnetic field strength.

Answer 1

The Correct Option is A

The torque \( \tau \) experienced by a rectangular coil of area \( A \) in a magnetic field \( B \) is given by: \[ \tau = A B \sin \theta \] Where: - \( A = l \times b \) is the area of the coil, - \( \theta \) is the angle between the normal to the coil and the magnetic field direction. If the coil is placed perpendicular to the magnetic field, \( \sin \theta = 1 \).
Thus, the torque is: \[ \tau = l b B \]
Thus, the correct answer is \( l b B \).